There is a software called "Nevitum". Rated 5 stars on Cnet. It may be primarily invoice but I am unsure. It works with 10.5 and is FREE. It seems that it is updated seeing as the last update was early September, 2011. ;)

You can check out **Handdy.com**. It comprises of both the bookkeeping and invoicing software in a single suite, and is of free. Its compatible with both, your PC and MAC. You can check this out (if required), as you're not to lose your pennies out there.